Radio frequency (RF) transceivers may comprise integrated circuit chips with RF connections or inter-chip links between them. An RF output driver circuit is commonly employed to provide the RF signal on the inter-chip link. In millimeter-wave (mmw) 5G transceivers, such an RF inter-chip link may operate at high frequencies, such as, for example, 10-20 gigahertz (GHz), and commonly needs very wide bandwidth, such as, for example, 6-12 GHz. An RF inter-chip link in a receiver also commonly needs to carry high power. Impedance matching is commonly employed for robust performance of both chips. The impedance matching may be passive or active.
Passive impedance matching techniques are commonly characterized as either tunable or wideband. Both tunable passive impedance matching and wideband passive impedance matching may incur a chip area penalty and introduce significant temperature sensitivity. Tunable passive impedance matching may reduce bandwidth. Wideband passive impedance matching may increase loss. Also, both tunable and wideband impedance matching may carry a trade-off between mismatch and linearity over wide bandwidths or tuning ranges.
Active impedance matching may also be employed. An active impedance matching circuit may be based on, for example, a source follower transistor configuration. However, a conventional source follower configuration may adversely impact linearity and power consumption. Also, an RF output driver based on a source follower may present a high impedance to preceding amplification stages, resulting in high voltage swings.
It would be desirable to provide an RF output driver having a low input impedance and matched output impedance, low current, and/or good linearity.